Php experts lead the way--summary and answers to questions_PHP tutorial

1: Why can’t I get the variable

I POST data name from one web page to another web page, why can’t I get any value when I output $name?

In PHP4.2 and later versions, register_global defaults to off
If you want to get the variables submitted from another page:

Method 1: Find register_global in PHP.ini and set it For on.
Method 2: Put this extract($_POST);extract($_GET);(note that there must be Session_Start() before extract($_SESSION)) at the front of the receiving web page.
Method 3 :Read variables $a=$_GET["a"];$b=$_POST["b"] one by one. Although this method is troublesome, it is safer.

　2: Debugging your program

You must know the value of a certain variable at runtime. This is what I did, create a file debug.php with the following content:

PHP code:

Ob_Start();
Session_Start();
Echo "

"

;

Echo "The _GET variables obtained on this page are: ";
Print_R($_GET);

Echo "The _POST variables obtained on this page are: ";
　Print_R($_POST);

　Echo "The _COOKIE variable obtained on this page is :";
　Print_R($_COOKIE);

Echo "The _SESSION variables obtained on this page are: ";
　Print_R($_SESSION);

Echo "";
　?>

Then set include_path = "c:/php" in php.ini, and put debug.php in this folder. You can include this file in each web page in the future and view the obtained variable names and values. .

　3: How to use session

For anything related to session, the function session_start() must be called before;

Paying value for the session is very simple, such as:

PHP code:

　Session_start();
　$Name = "This is a Session example";
Session_Register("Name");//Note, do not write: Session_Register("$Name");
Echo $_SESSION["Name"];
//Then $_SESSION["Name"] is "This is a Session example"
　?>

After php4.2, you can pay directly for the session Value:

PHP code:

🎜>　$_SESSION
[
"name"]="value"; 　?> Cancel the session as follows:
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PHP code:

　 session_start();
session_unset();
session_destroy();
　?>

There is a BUG in canceling a session variable in php4.2 and above.

　Note:

　1: There cannot be any output before calling Session_Start(). For example, the following is wrong.
　============ ==============================
1 line
2 lines 3 lines Session_Start( );//There was already output in the first line before
4 lines....
5 lines?>
================= =========================

Tip 1:

Whenever ".... ....headers already sent..... ", which is the information output to the browser before Session_Start(). If you remove the output, it will be normal. (This error will also occur in COOKIE, and the cause of the error is the same )

Tip 2:

If your Session_Start() is placed in a loop statement and it is difficult to determine where the information was output to the browser before, you can use the following method:
Line 1
　...Here is your program...

2: This What is the error

Warning: session_start(): open(/tmpsess_7d190aa36b4c5ec13a5c1649cc2da23f, O_RDWR) failed:....
Because you did not specify the storage path of the session file.

Solution:
　(1) Create the folder tmp in the c drive
　(2) Open php.ini, find session.save_path, and change it to session.save_path= "c:/tmp"


4: Why when I send variables to another web page, I only get the first half, and all the ones starting with spaces are lost

PHP code:

　　$Var="hello php";//Change to $Var= " Hello php"; Try to get what result
　$post= "receive.php?Name=".$Var;
header("location:$post") ;
　?>

Content of receive.php:

PHP code:

　 Echo "

"

;
Echo $_GET ["Name"];
　Echo "";
　?>

The correct method is:

PHP code:

🎜>　$Var
="hello php";
　$post= "receive.php?Name=".urlencode($Var);
　header("location:$post");
　?>
You don’t need to use Urldecode() on the receiving page, the variables will be automatically encoded.

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5: How to intercept Chinese characters of a specified length without appearing "?>" ends, and the excess part is replaced by "..."

Generally speaking, the variables to be intercepted come from Mysql. First, make sure that the field length is long enough, usually char ( 200), can hold 100 Chinese characters, including punctuation.
PHP code:

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